"Usually you will receive the order confirmation a few minutes after the purchase. In the case of an electronic good, the confirmation already contains all download links and activation codes (serial number). If you have not received a confirmation email for your purchase, the email may have been marked as spam. Check your spam folder for the email. If the email cannot be found in the spam / junk folder, please contact Support. Please note also the order number." (Adapted from here.)
@vkmast 's advice is good if you purchased online from vegascreativesoftware.com . Based on my recent experience, if you purchased from a third party reseller then you may receive an order confirmation shortly after purchase but it may take a couple of days before you receive an email with the activation code - particularly if there is a weekend involved.